Disclosed is a way of enhancing capabilities of an interface, such as a communications bus (100), while retaining backwards compatibility of the interface. The bus has a plurality of signal lines (250) including critical control signal lines. Legacy devices (102-103) present a legacy interface to each other over the bus by communicating with each other via a legacy protocol (251) over the bus. Critical control signals of the legacy protocol are conveyed by the critical control signal lines. New devices (104-105) present an enhanced interface to each other over the same bus by communicating with each other via an enhanced protocol (252) over the bus. Control signals of the enhanced protocol are conveyed by signal lines other than the critical control signal lines for the legacy protocol, so that the critical control signal lines remain idle or invalid for the legacy protocol. The new devices signal to each other an intent to use the enhanced protocol by sending a signal on a signal line (253) that is not used by the legacy protocol. The new devices preferably can communicate on the bus via either protocol, and thus can communicate not only with each other but also with the legacy devices.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An apparatus comprising: a first device for coupling to a second and a third device via a physical connection that is common to all three said devices, wherein the second device presents a first interface to the first device over the connection, the first interface comprising signals on the connection having at least one of a first meaning and a first form, and the third device presents a second interface different from the first interface to the first device over the connection, the second interface comprising the signals on the connection having at least one of a second meaning and a second form different from the first meaning and the first form, respectively; and an interface arrangement of the first device, for effecting and presenting the first interface to the second device on the connection and effecting and presenting the second interface to the third device on the connection; wherein the second interface provides capabilities different from those provided by the first interface.
2. The apparatus of claim 1 wherein: the second interface provides capabilities greater than capabilities provided by the first interface.
3. The apparatus of claim 1 wherein: the second interface provides capabilities that cannot be provided by the first interface.
4. The apparatus of claim 1 wherein: the interface arrangement uses a first communications protocol on the connection to provide the first interface and uses a second communications protocol, different from the first protocol, on the connection to provide the second interface.
5. The apparatus of claim 4 wherein: the connection comprises a plurality of signal lines; and signals conveyed across individual said lines by the second protocol differ from signals conveyed across same said individual signal lines by the first protocol.
6. The apparatus of claim 5 wherein: each said protocol comprises a plurality of signals including critical control signals; the critical control signals of the first protocol are conveyed by first critical control signal lines of the connection; and the control signals of the second protocol including the critical control signals of the second protocol are conveyed by signal lines of the connection other than the first critical control signal lines.
7. The apparatus of claim 1 wherein: the first device includes means for signalling use of the second interface to the third device.
8. The apparatus of claim 7 wherein: the connection comprises a plurality of signal lines; and the signalling means sends a signal signalling the use of the second interface across a signal line not used by the first interface.
9. The apparatus of claim 7 wherein: the signaling means sends across the connection a signal not used by the first interface and signalling the use of the second interface.
10. The apparatus of claim 7 wherein: the signalling means sends across the connection a signal that is not recognized by the first interface and signalling the use of the second interface.
11. A method of interfacing a first device to a second device and a third device via a physical connection that is common to all three said devices, comprising: the second device presenting a first interface to the first device over the connection, the first interface comprising signals on the connection having at least one of a first meaning and a first form; the third device presenting a second interface different from the first interface to the first device over the connection, the second interface comprising the signals on the connection having at least one of a second meaning and a second form different from the first meaning and the first form, respectively; the first device presenting the first interface to the second device and presenting the second interface to the third device over the connection; wherein the second interface provides capabilities different from capabilities provided by the first interface.
12. A device connectable to a common communications bus having a plurality of signal lines for conducting a first set of signals, including first control signal lines for conducting control signals of the first set of signals, the device including: first means for transmitting or receiving the first set of signals on the signal lines, including individual signals having at least one of a first meaning and a first form; and second means for transmitting or receiving a second set of signals on the signal lines, including the individual signals having at least one of a second meaning and a second form different from the first meaning and the first form, respectively, including transmitting and receiving control signals of the second set of signals, on the signal lines other than the first control signal lines; whereby the device is able to communicate on the bus with devices that communicate exclusively via the first set of signals as well as with devices that communicate via the second set of signals.
13. The device of claim 12 in combination with: the communications bus; at least one device that communicates via the first set of signals; and at least one device that communicates via the second set of signals.
14. A method of communicating between three devices connected by a communications bus common to the three devices and having a plurality of signal lines including first critical control signal lines, comprising: a first one and a second one of the three devices communicating with each other by transmitting and receiving exclusively signals of a first set of signals on the signal lines of the bus, including individual signals having at least one of a first meaning and a first form, including transmitting and receiving critical control signals of the first set of signals on the first critical control signal lines; and the first one and a third one of the three devices communicating with each other by transmitting and receiving signals of a second set of signals on the signal lines of the bus, including the individual signals having at least one of a second meaning and a second form different from the first meaning and the first form, respectively, including transmitting and receiving control signals of the second set of signals on signal lines other than the first critical control signal lines.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
April 9, 1999
June 3, 2003
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